Intrathecal IgG synthesis in multiple sclerosis and other neurological diseases: a comparative evaluation by IgG-index and isoelectric focusing.

Intrathecal IgG synthesis has been investigated by determining the IgG index and by isoelectric focusing in 30 cases of definite multiple sclerosis, in 15 cases of probable multiple sclerosis and in 128 patients affected by other neurological diseases. The blood-brain barrier function was evaluated at the same time by serum albumin/CSF albumin quotient and isoelectric focusing. The IgG index was found elevated in 73.3% of definite multiple sclerosis patients, while oligoclonal IgG bands occurred in 90%. In the other neurological diseases the IgG index was abnormally increased in 35.1% but IgG bands were present only in cerebrospinal fluid (CSF) in 1.5% and both in the CSF and serum in 7% of patients. The high capacity of isoelectric focusing to detect IgG oligoclonal bands in the CSF is pointed out as an extremely useful diagnostic tool in multiple sclerosis.